It's a Signal Crayfish I suspect, an import from the US:
As far as I remember, they did some repairs to the banks of the New River section by the (currently closed) path into Finsbury Park a few years ago, due to the damage done by these crayfish.
More on this in Harringay here.
A fabulous photo!
Eye-opening. I had never heard of Signal Crayfish and wouldn't have expected to find anything of the sort around here.
British waters for British shellfish I say!
As others have said, likely a signal crayfish, and thus an invasive species which you are thus permitted to catch (possibly within the bounds of needing a usual fishing licence).
I went and caught some near Oxford many years ago - bit of liver on a rudimentary chickenwire net stretched over a coat hanger got us a decent half bucket over a couple of hours. Tasty, despite their unwanted presence in UK waterways.
Great Crayfish picture, I love it!
American Signal Crayfish! Are an invasive species that destroy rivers, they can be eaten but best stamped on. The River Authorities will tell you this! Must be eradicated.
Live and let live, that's what I say.
Problem is that they have pretty much wiped out our native crayfish. Same as the imported squirrels vs the native reds.
Well yes, I suppose that is a problem.